Electric charges: attraction and repulsion
The pull and the push inside every atom
1. Electric charges: attraction and repulsion: from zero
2. A pull and a push
From Cr to Cu, the atoms gain protons but hardly change size. What is pulling, and what is pushing?
Start with the basics. Predict:
Pick the right answer
Two electrons are close to each other. What happens?
- A. They attract each other
- B. They repel each other
- C. Nothing happens, because electrons are too small
Explanation
Both electrons carry a negative charge, and like charges repel, so the two electrons push each other apart.
3. Like charges repel, unlike charges attract
Electric charges
There are two kinds of charge, positive (+) and negative (−). Like charges repel; unlike charges attract.
In an atom, the protons in the nucleus are positive and the electrons are negative. So the nucleus attracts the electrons.
4. Stronger or weaker?
Change the charge of the nucleus and the distance to the electron. Watch the pull.
Charge of the nucleus (number of protons) 3
Distance from the nucleus 2 units
Pull on the electron (to compare only) 75
Tried both sliders? Tap to see the pattern
- More charge → stronger attraction.
- Smaller distance → stronger attraction.
- The same two rules hold for the repulsion between two electrons.
5. Attract or repel?
Sort into groups
Sort each pair: do they attract or repel?
The nucleus and an electronTwo electrons in the same atomTwo protonsA proton and an electron far apart
Pick the right answer
Atom X has 11 protons and atom Y has 17 protons. Their outer electrons are at about the same distance from the nucleus. Which nucleus pulls its outer electrons more strongly?
- A. X, because it has fewer protons
- B. Y, because its nucleus has more positive charge
- C. Both pull equally, because the distance is the same
Explanation
With the distance fixed, more protons means a stronger nuclear attraction.
Need a hint?
- The distance is the same, so only one thing differs.
- More protons means more positive charge in the nucleus.
6. Summary
- Like charges repel; unlike charges attract.
- More charge or less distance means a stronger force.
- In an atom, the nucleus attracts the electrons; the electrons repel each other.
Can you explain why adding more electrons to the same atom makes them push each other apart?
Reveal
All electrons carry a negative charge, and like charges repel. So the electrons in an atom push each other apart, and more charge means a stronger force.